The House is consumed this week with the upcoming GOP leadership elections in the wake of Majority Leader Eric Cantor's primary defeat, but Oversight and Government Reform Chairman Darrell Issa doesn't want that reality to take the pressure off the IRS.

The California Republican is plowing ahead with his panel's year-long investigation into alleged misconduct at the IRS in its targeting of certain conservative outside groups applying for tax-exempt status. In the midst of push-back from Democrats who say the investigation has become a partisan witch hunt, Issa has been emboldened by new revelations that key emails of ex-IRS official Lois Lerner have gone missing. While the agency says the IRS emails were lost in a computer crash, Issa and other Republicans say that excuse sounds too convenient, given that Lerner has been a main target in the House GOP's probe. Congress went so far as to recently hold her in contempt for refusing to testify on her role in the controversy.

So on Tuesday afternoon, Issa announced that his committee had handed IRS Commissioner John Koskinen a subpoena for documents "related to the recent revelation that the IRS supposedly 'lost' former IRS official Lois Lerner's emails for a two year period, January 2009 to April 2011."

The subpoena also covers Lerner's hard drive, electronic devices and documents "connected to the IRS's response to Congress."

Koskinen himself was already subpoenaed on Monday to testify before the Oversight and Government Reform Committee on the evening of June 23.

Issa had this to say on Tuesday regarding the whole matter:

“After a year of beating down efforts by the Obama Administration and its allies to obstruct an investigation into targeting, the IRS now says it lost perhaps the most critical evidence. When Commissioner Koskinen testified before the Committee in February, he made no mention of this. It was only earlier this month, during an interview with a Justice Department official, that the Oversight Committee learned about the existence of subpoenaed 2010 Lerner e-mails that the IRS had not produced. While this apparently forced the IRS to cough up an admission, we still do not have answers about how and why the IRS tried to deceive Congress about these missing e-mails. This subpoena seeks those answers.”